Abstract: Members of the elusive insect order Embiidina are known for their prolific use of
silk, and are unusual among insects in that silk is produced by both sexes and all
life stages. However, the relative costs of silk spinning might vary considerably
between the sexes, as male embiids do not feed as adults and are thus expected
to be more resource-limited than females, which feed continuously throughout
their lifetimes. Previous research on this group has also shown that the tarsal silk
glands of male embiids contain significantly larger silk reservoirs than those of
females, and it has been suggested that juvenile males may use these enlarged
reservoirs to store silk proteins for use during adulthood, when the amount of
energy available for silk production is low. The purpose of this study was to
evaluate the plausibility of these conclusions by comparing the silk spinning
behaviors of immature male and female embiids in the Indian species Aposthonia
ceylonica (Enderlein, 1912) (Embiidina: Oligotomidae). Since this species is
gregarious, spinning was also examined in a group context in order to test the
hypothesis that males can adjust the amount of silk production in response to group composition, as they may be expected to conserve their own silk in the
presence of spinning females. The quantity of silk produced and the amount of
time spent spinning were measured over 24 hours for solitary late instar male
and female nymphs, as well as for nymphs in single sex and mixed sex groups.
The results of this study suggest that juvenile males do produce significantly less
silk than juvenile females, but no significant differences were found between
groups and solitary individuals or between single sex and mixed sex groups.
These findings corroborate the suggestion that males store silk as juveniles,
which is likely a strategy to compensate for limited energy availability during
adulthood. However, the data do not provide any evidence for social contextdependent
silk spinning in the Embiidina. This study is among the first to address
these questions in this little-studied insect order, but further research which
incorporates more species of embiids as well as field observations is necessary
to fully assess sex-related differences in silk production.